By P.G. LeFevre
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Extra resources for Active Transport through Animal Cell Membranes
However, the action of the intracellular K + level is probably not so much on phosphate-transfer processes as on synthetic activities; the incorporated P is not readily lost again, more than a mere translocation being involved. Glucose, fructose. or galactose assist in the phosphate uptake in this system, but G-l-P, G-b-P. or F-b-P are not effective. Table X. Phosphate Uptake and :lletabolic Activity in Bremer's Yeast. (Modified from NICKERSON. ) Additions to glucose· phosphate medium Uptake (arbitrary units) p32 I I I I· None DNP, 5· 10-~ M.
The double treatment given to K + in the kidney tubule probably involves different loci. In a recent review of the subject, MUDGE (1954) calls attention to the micropuncture work of Bott on the Necturus kidney, whidl shows directly that the filtered K + is actually nearly completely reabsorbed in the proximal tubule, only to be replaced by active tubular secretion in the distal tubule. -According to CONWAY, FITZGERALD, and MACDOUGALD (1946), the proximal tubular cells of the isolated frog kidney can accumulate very high concentrations of K+ when an excess of this ion is supplied in the medium; but these cells are essentially impermeable to Na+, thus falling into the BOYLE-CONWAY pattern as originally developed for muscle cells.
Both pyruvate and ATP. 05 Anaerobic; no addition pyruvate, 5 mM. . . ATP, lmM . . . both pyruvate and ATP. 37 "Cyclophorase" (nuclei and mitochondria) Mitochondria Untreated; 0° C . ketogluterate, 5 mM. . and incubated 15 min. at aerobically . anaerobically . . . 1 0° C.. . :Wu C. . Na+ is here removed from medium, while almost none is lost from particles. "Cyclophorase" preparations all incubated 30 minutes at 20°C. 5 mM. ~aHC03 STANBURY and MUDGE (1953) attempted to analyse the relation of the mitochondrial K+ maintenance to the metabolic activity in similar preparations from rabbit liver.
Active Transport through Animal Cell Membranes by P.G. LeFevre